Vbab, sorry to hear that things aren't going so well - I guess it's easy in the day-to-day slog of being parents to get into ruts and forget to take time for each other. Does DH know how you are feeling? Don't know your family circumstances, but is there any way you could offload DS for a night with a grandparent, and MAKE SURE you do something grown up together (i.e. a nice meal/bottle of wine/video/chat, before anyone lowers the tone)
If you can't/don't feel up to not having LO for a night, what about still planning the above, but after DS's in bed? Not quite the same as you won't get a long lie, but it's amazing what taking the effort to focus on each other will do, and sustain you when you both start to slip into old ways again. Take it from one who's been there!!!
My best pal is getting married in September and DH and I have arranged to stay overnight at the hotel with my parents coming to our house to look after the kids. It'll be the first night off since DD was born, and you have no idea how the anticipation is keeping me going....
As for his sleeping, not sure. Is he looking sleepy when he goes down? DD started getting a wee bit clingy and objected to me leaving the room. If they're still sleepy, best not get into bad habits that'll then be difficult to break. Be firm, pat, shush, comfort, but don't start picking up/walking the room etc, or you'll see even less of DH than you are just now!
Hope you get things sorted out on all counts.